Conventionally, for the inner liner disposed as an air barrier layer on an inner surface of a tire for maintaining internal pressure of the tire, a rubber composition mainly made of butyl rubber or halogenated butyl rubber have been used. However, since the rubber composition mainly made of the butyl rubber has a low air barrier property, when the rubber composition is used for the inner liner, the inner liner needs to have a thickness of around 1 mm. Therefore, a weight ratio of the inner liner occupying the tire accounts for about 5%, which has been obstructing weight reduction of the tire for improving fuel efficiency of automobiles, agricultural vehicles, construction work vehicles and the like.
On the other hand, ethylene-vinyl alcohol copolymer (hereinafter, it may be abbreviated as EVOH) is known to have an excellent gas barrier property. Since an air transmission amount of the EVOH is hundredth part or less than that of the rubber composition used for a butyl-based inner liner, an inner liner made of EVOH with a thickness of 100 μm or less may significantly improve internal pressure retention of the tire and, simultaneously, enables weight reduction of the tire.
There are many resins with air permeability lower than that of butyl rubber. However, when the air permeability of the resin is about one tenth of that of the butyl-based inner liner, the inner liner needs to have a thickness greater than 100 μm, otherwise there is only a small effect of improving the internal pressure retention. On the other hand, when the inner liner has a thickness greater than 100 μm, there is only a small effect of reducing a tire weight and, moreover, the inner liner breaks or generates cracks due to deformation at the time of tire bending, making it difficult to maintain the barrier properties. Although there is disclosed a technique that, in order to improve bending resistance, uses elastomer in which a nylon resin with a melting point at 170-230° C. contains a halide of isobutylene-paramethylstyrene copolymer (Patent Document 1), there is a problem that, due to a high ratio of the elastomer with respect to the resin, while the bending resistance is improved, the barrier property of the nylon resin may not be maintained.
On the other hand, when the above EVOH is used, since the inner liner with a thickness of 100 μm or less may be used, the inner liner hardly breaks or generates cracks by bending deformation at the time of tire rolling. Therefore, it can be said that using EVOH for the inner liner of the tire in order to improve the internal pressure retention of the pneumatic tire is effective. For example, Patent Document 2 discloses a pneumatic tire comprising an inner liner made of EVOH.
Also, Patent Document 3 discloses that it is preferable to use an inner liner in which, in order to improve the internal pressure retention of a tire, an auxiliary layer made of elastomer adheres via an adhesive layer.
However, because of low adhesiveness between a resin film layer containing thermoplastic resin and a rubber-like elastic layer, there has been room for improvement in a peel-off effect.
Therefore, Patent Document 4, in order to improve the peel-off effect, discloses a laminated product having an adhesive layer composed of an adhesive composition (I) obtained by compounding, with respect to 100 parts by mass of a rubber component, 0.1 part by mass or more of at least one of maleimide derivative (H) having two or more reactive sites in molecules and poly-p-dinitrosobenzene.